Video skips frames unpredictably in Pavlovia

Online experiments
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21

Hi @sotiri,

thank you for your reply.

I had a look at the recording you sent me (on QuickTime player) and I see there are two sorts of problems: first, the duration of each video is shorter than it should be (but you might have reduced it on purpose), and, second, I can see glitches in all of them. In other words, this is a perfect visualization of what looks wrong in my study (i.e., the impression of motion is not as smooth as it is in the original videos + the duration of the videos is not always the same).

22

Hi @aurelio.bruno, OK great, thanks for confirming. The word trim in the filename is in reference to something different, I let the experiment playback times unchanged. Would it be possible to please review the screen recording below for any like glitches? Playback in this case is done outside the browser completely. Thanks,

23

Hi @sotiri, this is even worse. The duration is further reduced. These presentations are just brief flashes with no motion in them. They look like static single frames of my videos.

Cheers,

Aurelio

24

Hi @aurelio.bruno, OK thanks for confirming, would you agree that if video playback straight from disk turns up problematic, the cause is likely unrelated to PsychoJS and probably not a bug on our end? Could this not be an encoding issue?

25

Hi @sotiri,

if that’s the case, shouldn’t we see glitches in the .mp4 videos as well, when played with a movie player (Quicktime, for example)?

Also, I tried to create the videos both in Psychopy and using Psychtoolbox (using the h.264 encoding, as suggested on the forum), and there were glitches in both when played online in Pavlovia.

So, if it is an encoding issue, I don’t really understand where it might come from.

26

Hi @aurelio.bruno, that would be the reason I made those screen recordings for you to confirm, the playback is done through html5 video and QuickTime respectively. Bizzare non?

27

Hi @sotiri,

oh, that’s quite crazy. The mp4 videos for my study work perfectly fine on my QuickTime player.

28

Hi @aurelio.bruno, OK thought so, to double check, would it be possible to send me a .zip of all or some of the videos without going through git or Pavlovia? Thanks, x

29

Sure. I can’t apparently upload a zip file here, so, I’m sending you some of them, but they all have the same duration and, essentially, the same characteristics.

30

Alright, cool, thanks, those videos are definitely different, because the background for the ones inside the repo seems to be black for some reason, e.g.,

31

Yes, I had changed the colour of the background and of half of the dots after you saw the first version, so that’s why they look different now.

32

I think I have a similar problem…with no good solution so far (sorry). My videos are much longer (up to 10 seconds) and they glitch a lot, get stuck on some frames, and ugly stuff like that. They actually run more or less smoothly on Firefox, but only when the browser window is not too big (maybe the resizing/upsizing of the videos might be a big part of the problem here), but it’s horrible on Chrome. Have you also tried different browsers and different browser window sizes?

33

Hi there,

thanks, yes, I have tried with different browsers and different operating systems. My study doesn’t seem to work at all on Chrome or on some versions of Windows. It runs fine on Firefox, with the aforementioned occasional glitches.